Collapse of nearly spherical domain walls

The collapse of nearly spherical domain walls is studied in the thin-wall approximation. Perturbations away from spherical symmetry are damped during the initial stages of collapse. However, these perturbations grow during the final stages of collapse. The question of whether the shape of the wall during its final stages of collapse is spherical, cigarlike, or pancakelike depends on its initial shape and on the ratio of the thickness of the wall to its initial size.